1. Field of the Invention
The present invention relates to a backlight unit and a liquid crystal display employing the same and, more particularly, to a direct light type backlight unit having a sequential division lighting structure of division areas, and a liquid crystal display employing the same.
2. Description of the Related Art
A liquid crystal display (LCD), which is a type of flat panel display, is a light receiving type display that is not self-luminescent but forms an image using incident light from an outside source. A backlight unit is disposed at a rear of the LCD to irradiate light toward a liquid crystal panel.
A cold cathode fluorescence lamp (CCFL) is generally used as a light source of the backlight unit of the LCD. However, the CCFL has a comparatively short lifetime and a low color reproducibility. The CCFL is much more disadvantageous with respect to lifetime and color reproducibility than a light emitting diode (LED) and is also more disadvantageous in instant lighting than an LED.
Since the CCFL is poor at instant lighting, it is difficult to employ a backlight unit using the CCFL as a light source in a time-division LCD. The time-division LCD requires a backlight unit that can be division lighted to synchronize with a picture scanning time. A backlight unit using an LED as a light source can satisfy such a requirement.
The backlight units are generally classified, depending on the arrangement of light source, into direct light type backlight units in which light emitted from a plurality of light sources disposed right below a liquid crystal panel is irradiated toward the liquid crystal panel, and edge light type backlight units in which light emitted from a light source disposed on a sidewall of a light guide panel (LGP) is transmitted to a liquid crystal panel.
The direct light type backlight units may use, for example, an LED as a point light source. In the direct type backlight unit using the LED as a point light source, LEDs are arranged in a two-dimensional array. Especially, the LEDs are arranged in plural lines, each line having a plurality of LEDs arranged in a line.
The direct light type backlight unit using the LEDs as a light source can be used in a time-division LCD. Such a direct light type backlight unit is provided with a diffusion plate for diffusing light diverging from the LEDs to irradiate the diffused light toward a liquid crystal panel.
In the time-division LCD employing the direct light type backlight unit using the LEDs as a light source, the lighting areas of the LEDs are divided and the lighting areas of the LEDs are lighted in synchronization with a scan time of the liquid crystal panel.
However, in a case where light diverging from a selected one of the divided lighting areas invades an adjacent lighting area through the diffusion plate, when one picture is changed to another one, it is difficult to effectively remove the motion blur phenomenon such that an after-image remains.